Combining fossilized skeletons and cutting-edge animation, this film excites and educates by re-enacting one of the greatest evolutionary dramas in the planet's long history.

A herd of 150-foot-long, 100-ton Argentinosaurs plods across the dry plains on redwood-sized legs trampling everything in its path. A 16,000-pound mother Giganotosaur gently scoops a hatchling called Long Tooth into her cavernous mouth to protect it from predators. Far away in space, a comet hurtles toward Earth en route to end the dinosaurs' 180-million-year reign in an apocalyptic blast.

The real star is the film's success visualizing an overgrown Mesozoic world when giant reptiles ruled the planet.

Barney would be just a purple hors d'oeuvre in this inhospitable time and place, which is actually present-day Argentina.

"Dinosaurs" alternates between the distant past and today by following paleontologist Rodolfo Coria, director of a dinosaur museum in Plaza Huincul, Argentina.

Considered the world's leading dinosaur expert, he has discovered 12 new species including Argentinosaurs and Giganotosaurs, the largest plant- and meat-eating creatures that ever lived.

As the film's primary non-saurian character, the sinewy Coria looks perfectly at home uncovering fossilized bones or striding across the rocky hills. When he and his team check out enormous footprints stamped into volcanic rock, the reality of the dinosaur's name - Terrifying Lizard - strikes home.

Part detective story, part family drama, "Dinosaurs" is a sort of Stone Age "Sopranos" in which house-sized herbivores and smaller but ferocious carnivores compete for top spot in the prehistoric food chain.

And what a supporting cast of armor-plated, long-necked, saber-toothed and plug-ugly characters.

Pterodaustro was a flying reptile with 500 teeth. Unenlagia was a feathered predator who snuck around stealing eggs. And Liopleurodon was a 150-ton marine reptile that could have turned Moby Dick into sushi.

Yet the vast rugged Patagonian landscape emerges as a fascinating character that provides clues to why so many dinosaur fossils are being found there.

Located in South America's southern tip, Patagonia extends from the Andes mountains to the Atlantic Ocean. Its vast expanses probably made it possible for huge creatures to thrive amid a dry climate and cold nights that likely kept cold-blooded dinosaurs alive.

Even when the dinosaurs fill the 6-story-high screen of the Simons IMAX Theatre, it's sobering to realize Argentinosaurs were more than twice as long as the 60-foot screen.

Directed by Marc Fafard, the film compresses 240 million years into a digestible but not dumbed-down version of evolutionary history by focusing largely on how two species, Argentinosaurs and Giganotosaurs, coped with their changing world.

During the Triassic Age 200 million years ago, all the Earth's continents formed a single land mass called Pangea. As land masses shifted over the eons, volcanos erupted, violent weather occurred and other changes created conditions suitable for dinosaurs.

Despite its tooth-and-claw realities, "Dinosaurs" is suitable for youngsters from 8 years old and up. The directors do not rub viewers' noses in gore, and the bloody attack on an Argentinosaur is carried off more tastefully than King Harold's death in "Shrek The Third."

When the 10-mile-wide comet crashes into the ocean off the Yucatan 65 million years ago, the film depicts the ensuing blast and lethal climactic changes as an ashen doomsday that hastened the end of the great beasts.